An armament from World War I has exploded at an industrial site in the former Flanders battlegrounds, killing two construction workers and injuring two more.

Johan Lescrauwaert of the Ypres prosecutor's office said a shell or grenade from the 1914-1918 war exploded near the workers. The circumstances were unclear because there was apparently no digging at the site - the usual cause of such accidents, he told VRT network.

Every year the battlefields in western Belgium throw up hundreds of armaments from the Great War, and most are destroyed without incident by a special Belgian army bomb squad. In a nearby city, the army was completing the destruction of over 800 gas canisters.

The Flanders battlefields cover dozens of cities where allies clashed with German forces for most of the war.